Display device

ABSTRACT

According to one embodiment, in a display device, one of the gate electrodes includes a first linear portion extending along the second direction, and a first projection portion projecting from the first linear portion and extending along the first direction, one of the first light shielding layers includes a second linear portion extending along the second direction, and a second projection portion projecting from the second linear portion and extending along the first direction, the first linear portion overlaps the second linear portion, the first projection portion overlaps the second projection portion, and the first projection portion and the second projection portion overlap at least one of the plurality of select lines.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of PCT Application No.PCT/JP2022/007937, filed Feb. 25, 2022 and based upon and claiming thebenefit of priority from Japanese Patent Application No. 2021-037461,filed Mar. 9, 2021, the entire contents of all of which are incorporatedherein by reference.

FIELD

Embodiments described herein relate generally to a display device.

BACKGROUND

Liquid crystal devices using a light shielding layer as a back gate havebeen developed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a display device.

FIG. 2A is a diagram illustrating a pixel of the display device.

FIG. 2B is a diagram illustrating a pixel of the display device.

FIG. 3 is a detailed circuit diagram of a signal line switch circuit ofan embodiment.

FIG. 4 is a plan view of the signal line switch circuit.

FIG. 5 is a plan view of a gate electrode of FIG. 4 .

FIG. 6 is a plan view of a light shielding layer.

FIG. 7 is a cross-sectional view of a transistor.

FIG. 8 is a plan view illustrating a part of FIG. 4 in an enlargedmanner.

FIG. 9 is a plan view illustrating a part of FIG. 4 in an enlargedmanner.

FIG. 10 is a plan view illustrating the gate electrode and the lightshielding layer.

FIG. 11 is a plan view illustrating another structural example of theembodiment.

FIG. 12 is a circuit diagram of a signal line switch circuit of FIG. 11.

FIG. 13 is a plan view of the gate electrode of FIG. 11 .

FIG. 14 is a plan view of the light shielding layer of FIG. 11 .

FIG. 15 illustrates a part of FIG. 11 in an enlarged manner.

FIG. 16 illustrates a part of FIG. 11 in an enlarged manner.

FIG. 17 is a plan view illustrates a structural example of a comparativeexample.

FIG. 18A is a plan view illustrating a gate electrode of a signal lineswitch circuit of FIG. 17 .

FIG. 18B is a plan view illustrating a light shielding layer of thesignal line switch circuit of FIG. 17 .

DETAILED DESCRIPTION

In general, according to one embodiment, a display device comprises

-   -   a plurality of signal lines;    -   a switch circuit connected to the signal lines; and    -   a plurality of select lines extending in a first direction and        arranged in a second direction, the plurality of select lines        being connected to the switch circuit, wherein    -   the switch circuit includes a plurality of transistors connected        to the plurality of the signal lines,    -   the plurality of transistors include a plurality of gate        electrodes and a plurality of light shielding layers overlapping        the plurality of gate electrodes,    -   each of the plurality of the select lines is connected to each        of the plurality of gate electrodes,    -   at least one of the gate electrodes includes a first linear        portion extending along the second direction, and a first        projection portion projecting from the first linear portion and        extending along the first direction,    -   at least one of the first light shielding layers includes a        second linear portion extending along the second direction, and        a second projection portion projecting from the second linear        portion and extending along the first direction,    -   the first linear portion overlaps the second linear portion,    -   the first projection portion overlaps the second projection        portion, and    -   the first projection portion and the second projection portion        overlap at least one of the plurality of select lines.

The present embodiment presents a display device which can improvecharacteristics of the signal line switch circuit.

Embodiments will be described hereinafter with reference to theaccompanying drawings. Note that the disclosure is merely an example,and proper changes within the spirit of the invention, which are easilyconceivable by a skilled person, are included in the scope of theinvention as a matter of course. In addition, in some cases, in order tomake the description clearer, the widths, thicknesses, shapes, etc., ofthe respective parts are schematically illustrated in the drawings,compared to the actual modes. However, the schematic illustration ismerely an example, and adds no restrictions to the interpretation of theinvention. Besides, in the specification and drawings, the same orsimilar elements as or to those described in connection with precedingdrawings or those exhibiting similar functions are denoted by likereference numerals, and a detailed description thereof is omitted unlessotherwise necessary.

The embodiments described herein are not general ones, but ratherembodiments that illustrate the same or corresponding special technicalfeatures of the invention. The following is a detailed description ofone embodiment of a display device with reference to the drawings.

In this embodiment, a first direction X, a second direction Y and athird direction Z are orthogonal to each other, but may intersect at anangle other than 90 degrees. The direction toward the tip of the arrowin the third direction Z is defined as up or above, and the directionopposite to the direction toward the tip of the arrow in the thirddirection Z is defined as down or below.

With such expressions as “the second member above the first member” and“the second member below the first member”, the second member may be incontact with the first member or may be located away from the firstmember. In the latter case, a third member may be interposed between thefirst member and the second member. On the other hand, with suchexpressions as “the second member on the first member” and “the secondmember beneath the first member”, the second member is in contact withthe first member.

Further, it is assumed that there is an observation position to observethe display device on a tip side of the arrow in the third direction Z.Here, viewing from this observation position toward the X-Y planedefined by the first direction X and the second direction Y is referredto as plan view. Viewing a cross-section of the display device in theX-Z plane defined by the first direction X and the third direction Z orin the Y-Z plane defined by the second direction Y and the thirddirection Z is referred to as cross-sectional view.

Embodiment

FIG. 1 is a circuit diagram of a display device. FIGS. 2A and 2Billustrate a pixel of the display device. FIG. 2A is a circuit diagramof a subpixel SX of FIG. 1 . FIG. 2B is a cross-sectional view of adisplay device DSP including the subpixel SX of FIG. 1 .

As in FIG. 1 , a display area DA of the display device DSP includes aplurality of pixels PX. Each of the pixels PX includes subpixel SXR,subpixel SXG, and subpixel SXB displaying red (R), green (G), and blue(B), respectively. Note that, a term subpixel SX is used when it is notnecessary to specifically distinguish the subpixel SXR, the subpixelSXG, and the subpixel SXB apart. As described above, each of thesubpixels SX is provided with a crossing point of each scan line GL andeach signal line SL. In other words, the subpixel SX is each providedwith an area defined by two adjacent scan lines GL and two adjacentsignal lines SL.

The scan lines GL extend in a first direction X and are arranged in asecond direction Y. The signal lines SL extend in the second direction Yand are arranged in the first direction X. The subpixels SX are arrangedin a matrix in the first direction X and the second direction Y.

As in FIG. 2A, each subpixel SX includes, for example, a switchingelement PSW, a pixel electrode PE, a common electrode CE, and a liquidcrystal layer LC. The switching element SW is formed of, for example, athin film transistor (TFT), and is electrically connected to the scanline GL and the signal line SL. The scan line GL is connected to theswitching element SW in each subpixel SX arranged in the first directionX. The signal line SL is connected to a switching element PSW in eachsubpixel SX arranged in the second direction Y. The pixel electrode PEis electrically connected to the switching element PSW. Each of thepixel electrodes PE is opposed to the common electrode CE, and drivesthe liquid crystal layer LC by a field generated between the pixelelectrode PE and the common electrode CE as above. Capacitance CS isformed, for example, between an electrode of same potential as thecommon electrode CE and an electrode of same potential as the pixelelectrode PE.

A source electrode of the switching element PSW of the subpixel SX isformed integrally with the signal line SL. Furthermore, each of thesignal lines SL corresponds to display data, and is connected to asignal line drive circuit SLC to which an image signal supplied to eachsubpixel SX is input. That is, the signal lines SL connect the subpixelsSX and the signal line drive circuit SLC.

Furthermore, a gate electrode GE of the subpixel SX is formed integrallywith the scan line GL. Furthermore, each scan line GL is connected to ascan line drive circuit GLC which supplies a scan signal to be suppliedto each subpixel SX in a one horizontal scanning time.

Now, referring to FIG. 1 , a connection relationship between the signalline SL and a signal line switch circuit ASW. In the example of FIG. 1 ,a signal lines SLR, a signal line SLG, and a signal line SLB aredisposed as a signal line SL to be connected to each of the subpixelsSX. The signal lines SLR, the signal lines SLG, and the signal lines SLBare connected to the signal line switch circuit ASW. The signal line SLRis a signal line connected to the red (R) subpixel SXR. The signal lineSLG is a signal line connected to the green (G) subpixel SXG. The signalline SLB is a signal line connected to the blue (B) subpixel SXB.

Specifically, the signal line SLR is connected to a subpixel columnincluding a plurality of subpixels SXR arranged in the second directionY. The signal line SLG is connected to a subpixel column including aplurality of subpixels SXG arranged in the second direction Y. Thesignal line SLB is connected to a subpixel column including a pluralityof subpixels SXB arranged in the second direction Y.

The signal line switch circuit ASW is a control circuit to supply asignal related to an image to the display area DA as the pixel circuit.The signal line switch circuit ASW includes a transistor STR, transistorSTG, and transistor STB as switching elements, and a select line SSR, aselect line SSG, and a select line SSB. The transistor STR, thetransistor STG, and the transistor STB are each a thin film transistor,for example. When it is not necessary that the transistor STR, thetransistor STG, and the transistor STB are specifically distinguished,it is referred to as a transistor ST. Furthermore, the signal lineswitch circuit ASW may be referred to as switch circuit.

The transistor STR is connected to the signal line SLR. The transistorSTG is connected to the signal line SLG. The transistor STB is connectedto the signal line SLB.

A drive element DD of FIG. 1 controls the signal line drive circuit SLC,scan line drive circuit GLC, and signal line switch circuit ASW based ondisplay controls signals such as display data, clock signal, displaytiming signal transmitted from the outside of the display device.

The transistor STR, the transistor STG, and the transistor STB are eachturned on/off by a switching signal output from the drive element DDthrough the select line SSR, the select line SSG, and the select lineSSB. The transistor STR is turned on/off by a switching signal inputthrough the select line SSR. The transistor STG is turned on/off byswitching signal input through the select line SSG. The transistor STBis turned on/off by a switching signal input through the select lineSSB.

The drive element DD controls turning on/off of the transistor STR, thetransistor STG, and the transistor STB of the signal line switch circuitASW according to the controlling of output of red image signal, greenimage signal, and blue image signal by the signal line drive circuit SLCin one horizontal period in a time divisional manner. That is, thetransistors ST (the transistor STR, the transistor STG, and thetransistor STB) included in the signal line switch circuit ASW are in arelationship to be driven in a time divisional manner. Specifically, animage signal from the signal line drive circuit SLC is input to a signalline SL connected to a transistor ST in an on-state through a extractingline WL amongst the transistor STR, the transistor STG, and thetransistor STB. Furthermore, the drive element DD controls the scan linedrive circuit GLC to maintain the on-state of the switching element PSWof a subpixel SX to which the image signal is written in a period ofoutputting image signals of respective colors.

Note that, the signal line switch circuit ASW may be referred to as RGBswitch, time division switch, analogue switch, or selector. Furthermore,in the present embodiment, one signal line switch circuit is disposedfor three signal lines connected to red, green, and blue subpixels;however, in some structure, one signal line switch circuit may bedisposed for two signal lines connected to two subpixels. Or, one signalline switch circuit may be disposed for six signal lines connected totwo pixels, that is, six subpixels. In that case, a signal line drivecircuit outputs an image signal in one horizontal period for six times.The number of time division can be optionally set based on, for example,write condition of the image signal to each subpixel or processing powerof the signal line drive circuit.

Note that, in a display period including the aforementioned horizontalperiod, a constant direct current voltage is supplied from a commonelectrode drive circuit CD to a switch circuit MUX through a line VDCL.The switch circuit MUX supplies the constant direct current voltage toall common electrodes CE through a common line CML. Thus, as describedabove, a field to drive the liquid crystal layer LC is generated betweenthe pixel electrode PE and the common electrode CE.

Now, referring to FIG. 2B, a cross-sectional structure of the displaydevice DSP including the subpixel SX will be explained. A firstsubstrate SUB1 includes a base BA1, a light shielding layer LS, aninsulating layer UC, a scan line GL, a signal line SL, a switchingelement PSW, an insulating layer HRCT, insulating layer HRC2, a commonelectrode CE, an insulating layer PAS, a pixel electrode PE, and analignment film AL1. The switching element PSW includes a semiconductorlayer SC, an insulating layer GI, a gate electrode GE formed integrallywith the scan line GL, an insulating layer ILI, and a source electrodeSE and a drain electrode DE formed integrally with the signal line SL,which are layered in the order stated above.

The base BA1 is a light transmissive substrate such as glass or flexibleresin substrate. The insulating layer UC is positioned above the baseBA1. The insulating layer GI is positioned above the insulating layerUC. The insulating layer ILI is positioned above the insulating layerGI.

The light shielding layer LS is formed between the base BA1 and theinsulating layer UC. The light shielding layer LS overlaps the scan lineGL (gate electrode) with the semiconductor layer SC interposedtherebetween. An edge portion of the light shielding layer LSsubstantially matches and an edge portion of the semiconductor layer SC.Thus, light emitted from the bottom side of the semiconductor layer SCcan be blocked, and light leakage of the switching element PSW can beprevented.

The insulating layer UC covers the light shielding layer LS. Thesemiconductor layer SC is opposed to the light shielding layer LS withthe insulating layer UC interposed therebetween.

The insulating layer UC, the insulating layer GI, the insulating layerILI, and the insulating layer PAS are inorganic insulating layers formedof an inorganic insulating material such as silicon oxide, siliconnitride, or silicon oxynitride. The insulating layer UC, the insulatinglayer GI, and the insulating layer ILI may have a monolayer structureusing the inorganic insulating material, or may have a multilayerstructure including the inorganic insulating material multi-layeredtherein.

On the other hand, the insulating layer HRC1 and the insulating layerHRC2 are organic insulating layers formed of an organic insulatingmaterial such as acrylic resin.

The semiconductor layer SC is disposed on the insulating layer UC. Thesemiconductor layer SC is formed of, for example, polycrystallinesilicon. However, the semiconductor layer SC of the present embodimentis not limited thereto. The semiconductor layer SC may be formed ofamorphous silicon or oxide semiconductor.

The scan line GL (gate electrode GE) is disposed on the semiconductorlayer SC and the insulating layer GI. The scan line GL is formed of ametal material such as aluminum (Al), titanium (Ti), silver (Ag),molybdenum (Mo), tungsten (W), copper (Cu), and chrome (Cr), or an alloyof a combination of aforementioned metal materials, and may have amonolayer structure or a multiplayer structure. In this example, thescan line GL is formed of a molybdenum-tungsten alloy.

The light shielding layer LS is formed of a light shielding metalmaterial. Specifically, the material used for the scan line GL issuitable, or a metal material which is different from those for the scanline GL may be adopted.

The signal line SL (source electrode SE) and the drain electrode DE arepositioned above the insulating layer ILI. The signal line SL isconnected to the semiconductor layer SC through contact holes of theinsulating layers GI and ILI. The drain electrode DE is connected to thesemiconductor layer SC through contact holes of the insulating layers GIand ILI. The signal line SL (source electrode SE) and the drainelectrode DE are formed of a metal material such as aluminum (Al),titanium (Ti), silver (Ag), molybdenum (Mo), tungsten (W), copper (Cu),and chrome (Cr), or an alloy of a combination of aforementioned metalmaterials, and may have a single layer structure or a multilayerstructure. In this example, the signal line SL (source electrode SE) andthe drain electrode DE have a multilayered body including a first layerincluding titanium (Ti), a second layer including aluminum (Al), and athird layer including titanium (Ti) layered in this order.

The insulating layer HRC1 covers the signal line SL, the drain electrodeDE, and the insulating layer ILI. An extracting electrode TE is disposedon the insulating layer HRC1, and is connected to the drain electrode DEthrough a contact hole of the insulating layer HRC1.

The extracting electrode TE is formed of the aforementioned metalmaterial or an alloy of a combination of the aforementioned metalmaterials, and may have a single layer structure or a multilayerstructure. In this example, the extracting electrode TE has amultilayered body including a first layer including titanium (Ti), asecond layer including aluminum (Al), and a third layer includingtitanium (Ti) layered in this order, or a multilayered body including afirst layer with molybdenum (Mo), second layer with aluminum (Al), andthird layer with molybdenum (Mo) layered in this order. The extractingelectrode TE is formed in the same line layer as with the common lineCML.

The insulating layer HRC2 is disposed to cover the insulating layer HRC1and the extracting electrode TE.

The common electrode CE and the relay electrode RE are positioned abovethe insulating layer HRC2. The relay electrode RE contacts theextracting electrode TE in a position overlapping therewith through acontact hole of the insulating layer HRC1. The common electrode CE andthe relay electrode RE are transparent electrodes formed of atransparent conductive material such as indium tin oxide (ITO) or indiumzinc oxide (IZO).

The insulating layer PAS overs the common electrode CE and the relayelectrode RE.

The pixel electrode PE is positioned above the insulating layer PAS andis connected to the relay electrode RE through a contact hole of theinsulating layer PAS. The pixel electrode PE is covered with thealignment film AL1. That is, the pixel electrode PE is disposed betweenthe insulating layer PAS and the alignment film AL1. The pixel electrodePE is a transparent electrode formed of the aforementioned transparentconductive material as with the common electrode CE.

The alignment film AL1 further covers the insulating layer PAS.

A second substrate SUB2 includes a base BA2, a light shielding layer BM,a color filer CF, an overcoat layer OC, and an alignment film AL2.

The base BA2 is a light transmissive substrate such as a glass or resinsubstrate as with the base BA1. The light shielding layer BM and thecolor filter CF are positioned in the base BA2 in the side opposed tothe first substrate SUB1.

The color filter CF includes a red color filter CFR, a green floorfilter CFG, and a blue color filter CFB.

The overcoat layer OC covers the color filter CF. The overcoat layer OCis formed of a transparent resin.

The alignment film AL2 covers the overcoat layer OC. The alignment filmAL1 and the alignment film AL2 are formed of a material with horizontalalignment characteristics.

The first substrate SUB1 and the second substrate SUB2 are arranged suchthat the alignment film AL1 and the alignment film AL2 are opposed toeach other. The first substrate SUB1 and the second substrate SUB2 areadhered by sealing while a certain cell gap is formed therebetween. Theliquid crystal layer LC is maintained between the alignment film AL1 andthe alignment film AL2. The liquid crystal layer LC is formed of apositive (positive dielectric anisotropy) liquid crystal material or anegative (negative dielectric anisotropy) liquid crystal material.

A polarizer PL1 is adhered to the base BA1. A polarizer PL2 is adheredto the base BA2. Note that, a retardation plate, diffusion layer, andreflection blocking layer may be included in addition to the polarizerPL1 and the polarizer PL2.

Furthermore, the display device DSP includes an illumination devicebelow the first substrate SUB1 which is not shown.

FIG. 3 is a detailed circuit diagram of the signal line switch circuitof the embodiment. The signal line switch circuit ASW of FIG. 3includes, as the select line SSR, the select line SSG, and the selectionline SSB, a select line SSR1, a select line SSG1, a select line SSB1, aselect line SSR2, a select line SSG2, a select line SSB2, a select linexSSR1, a select line xSSG1, a select line xSSB1, a select line xSSR2, aselect line xSSG2, and a select line xSSB2. To the select line xSSR1,the select line xSSG1, the select line xSSB1, the select line xSSR2, theselect line xSSG2, and the select line xSSB2, signals of oppositepolarity of the select line SSR1, the select line SSG1, the select lineSSB1, the select line SSR2, the select line SSG2, and the select lineSSB2. Note that, when it is not necessary to specifically distinguishthe select line SSR1, the select line SSG1, the select line SSB1, theselect line SSR2, the select line SSG2, the select line SSB2, the selectline xSSR1, the select line xSSG1, the select line xSSB1, the selectline xSSR2, the select line xSSG2, and the select line xSSB2 apart, theymay be referred to as a select line SS. The select lines SS extendsalong the first direction X and are arranged in the second direction Y.

The signal line switch circuit ASW of FIG. 3 includes, as the transistorSTR, the transistor STG, and the transistor STB, a transmission gateTGR11, a transmission gate TGG11, a transmission gate TGB11, atransmission gate TGR12, a transmission gate TGG12, a transmission gateTGB12, a transmission gate TGR21, a transmission gate TGG21, atransmission gate TGB21, a transmission gate TGR22, a transmission gateTGG22, and a transmission gate TGB22. Note that, when it is notnecessary to distinguish the transmission gates apart, they will bereferred to as a transmission gate TG. Transmission gates TG are each aCMOS transistor in which sources of an n-channel transistor and ap-channel transistor are connected to each other and drains thereof areconnected to each other as well.

The drain of the transmission gate TGR11 is connected to a signal lineSLR11 as a source of the signal line SLR11. The source of thetransmission gate TGR11 is connected to a connect line CNW1. A gateelectrode GERp11 as the p-channel transistor of the transmission gateTGR11 is connected to the select line xSSR1. A gate electrode GERn11 asthe n-channel transistor of the transmission gate TGR11 is connected tothe select line SSR1.

The drain of the transmission gate TGG11 is connected to a signal lineSLG11 as a source of the signal line SLG11. The source of thetransmission gate TGG11 is connected to a connect line CNW1. A gateelectrode GEGp10 as the p-channel transistor of the transmission gateTGG11 is connected to the select line xSSG1. A gate electrode GEGn11 asthe n-channel transistor of the transmission gate TGG11 is connected tothe select line SSG1.

The drain of the transmission gate TGB11 is connected to a signal lineSLB11 as a source of the signal line SLB11. The source of thetransmission gate TGB11 is connected to a connect line CNW1. A gateelectrode GEBp11 as the p-channel transistor of the transmission gateTGB11 is connected to the select line xSSB1. A gate electrode GEBn11 asthe n-channel transistor of the transmission gate TGB11 is connected tothe select line SSB1.

The drain of the transmission gate TGR21 is connected to a signal lineSLR21 as a source of the signal line SLR21. The source of thetransmission gate TGR21 is connected to a connect line CNW1. A gateelectrode GERp21 as the p-channel transistor of the transmission gateTGR21 is connected to the select line xSSR2. A gate electrode GERn21 asthe n-channel transistor of the transmission gate TGR21 is connected tothe select line SSR2.

The drain of the transmission gate TGG21 is connected to a signal lineSLG21 as a source of the signal line SLG21. The source of thetransmission gate TGG21 is connected to a connect line CNW1. A gateelectrode GEGp21 as the p-channel transistor of the transmission gateTGG21 is connected to the select line xSSG2. A gate electrode GEGn21 asthe n-channel transistor of the transmission gate TGG21 is connected tothe select line SSG2.

The drain of the transmission gate TGB21 is connected to a signal lineSLB21 as a source of the signal line SLB21. The source of thetransmission gate TGB21 is connected to a connect line CNW1. A gateelectrode GEBp21 as the p-channel transistor of the transmission gateTGB21 is connected to the select line xSSB2. A gate electrode GEBn21 asthe n-channel transistor of the transmission gate TGB21 is connected tothe select line SSB2.

The drain of the transmission gate TGR12 is connected to a signal lineSLR12 as a source of the signal line SLR12. The source of thetransmission gate TGR12 is connected to a connect line CNW2. A gateelectrode GERp12 as the p-channel transistor of the transmission gateTGR12 is connected to the select line xSSR1. A gate electrode GERn12 asthe n-channel transistor of the transmission gate TGR12 is connected tothe select line SSR1.

The drain of the transmission gate TGG12 is connected to a signal lineSLG12 as a source of the signal line SLG12. The source of thetransmission gate TGG12 is connected to a connect line CNW2. A gateelectrode GEGp10 as the p-channel transistor of the transmission gateTGG12 is connected to the select line xSSG1. A gate electrode GEGn12 asthe n-channel transistor of the transmission gate TGG12 is connected tothe select line SSG1.

The drain of the transmission gate TGB12 is connected to a signal lineSLB12 as a source of the signal line SLB12. The source of thetransmission gate TGB12 is connected to a connect line CNW2. A gateelectrode GEBp12 as the p-channel transistor of the transmission gateTGB12 is connected to the select line xSSB1. A gate electrode GEBn12 asthe n-channel transistor of the transmission gate TGB12 is connected tothe select line SSB1.

The drain of the transmission gate TGR22 is connected to a signal lineSLR22 as a source of the signal line SLR22. The source of thetransmission gate TGR22 is connected to a connect line CNW2. A gateelectrode GERp22 as the p-channel transistor of the transmission gateTGR22 is connected to the select line xSSR2. A gate electrode GERn22 asthe n-channel transistor of the transmission gate TGR22 is connected tothe select line SSR2.

The drain of the transmission gate TGG22 is connected to a signal lineSLG22 as a source of the signal line SLG22. The source of thetransmission gate TGG22 is connected to a connect line CNW2. A gateelectrode GEGp22 as the p-channel transistor of the transmission gateTGG22 is connected to the select line xSSG2. A gate electrode GEGn22 asthe n-channel transistor of the transmission gate TGG22 is connected tothe select line SSG2.

The drain of the transmission gate TGB22 is connected to a signal lineSLB22 as a source of the signal line SLB22. The source of thetransmission gate TGB22 is connected to a connect line CNW2. A gateelectrode GEBp22 as the p-channel transistor of the transmission gateTGB22 is connected to the select line xSSB2. A gate electrode GEBn22 asthe n-channel transistor of the transmission gate TGB22 is connected tothe select line SSB2.

A connect line CNW1 is connected to an extracting line WL1. A connectline CNW2 is connected to an extracting line WL2. Note that, when it isnot necessary to specifically distinguish between the connect line CNW1and the connect line CNW2, they will be referred to as a connect lineCNW. Furthermore, when it is not necessary to specifically distinguishbetween the extracting line WL1 and the extracting line WL2, they willbe referred to as an extracting line WL. Furthermore, in FIG. 3 , whenit is not necessary to specifically distinguish the gate electrodesapart, they will be referred to as a gate electrode GE.

In the signal line switch circuit ASW of FIG. 3 , six transmission gatesare electrically connected with respect to one extracting line WL. Thatis, image signals are input to six signal lines SL through oneextracting line WL.

FIG. 4 is a plan view of the signal line switch circuit. In the signalline switch circuit ASW of FIGS. 3 and 4 , the n-channel transistor ofeach of the transmission gates TGR11 and TGB11 is formed using asemiconductor layer SCn1. The n-channel transistor of each of thetransmission gate TGG21 and the transmission gate TGR21 is formed usinga semiconductor layer SCn2. The n-channel transistor of each of thetransmission gates TGB21 and TGG11 is formed using a semiconductor layerSCn3.

The n-channel transistor of each of the transmission gates TGG12 andTGB22 is formed using a semiconductor layer SCn4. The n-channeltransistor of each of the transmission gate TGR22 and the transmissiongate TGG22 is formed using a semiconductor layer SCn5. The n-channeltransistor of each of the transmission gate TGR12 and the transmissiongate TGB12 is formed using a semiconductor layer SCn6.

The p-channel transistor of each of the transmission gate TGR11 and thetransmission gate TGB11 is formed using a semiconductor layer SCp1. Thep-channel transistor of each of the transmission gate TGG21 and thetransmission gate TGR21 is formed using a semiconductor layer SCp2. Thep-channel transistor of each of the transmission gate TGB21 and thetransmission gate TGG11 is formed using a semiconductor layer SCp3.

The p-channel transistor of each of the transmission gate TGG12 and thetransmission gate TGB22 is formed using a semiconductor layer SCp4. Thep-channel transistor of each of the transmission gate TGR22 and thetransmission gate TGG22 is formed using a semiconductor layer SCp5. Thep-channel transistor of each of the transmission gate TGR12 and thetransmission gate TGB12 is formed using a semiconductor layer SCp6.

In the signal line switch circuit ASW of FIG. 4 , the light shieldinglayer LS is disposed to overlap each gate electrode GE. The lightshielding layer LS has a shape similar to the corresponding gateelectrode GE. FIG. 5 is a plan view of the gate electrode and the lightshielding layer of FIG. 4 . FIG. 5 is a plan view of the gate electrodeGE, and the gate electrode GE of the signal line switch circuit ASW ofFIG. 5 is in the same line layer as with the gate electrode GE of FIG.2B. FIG. 6 is a plan view of the light shielding layer LS, and the lightshielding layer LS of the signal line switch circuit ASW is in the sameline layer as with the light shielding layer LS of FIG. 2B. The lightshielding layer LS of FIG. 6 each corresponds to the gate electrode GEof FIG. 5 . For example, a light shielding layer LSGp21 of FIG. 6corresponds to a gate electrode GEGp21 of FIG. 5 . The light shieldinglayer LSGp21 has a shape similar to the gate electrode GEGp21, and theyoverlap with each other in a plan view. Note that, other light shieldinglayers LS and gate electrodes GE have a similar shape, and they overlapwith each other in a plan view.

When the gate electrode GE and the overlapping light shielding layer LSare shaped in a similar manner, capacitance of the gate electrode GE andcapacitance of the light shielding layer LS become the same. Thus,characteristics of the transmission gate and transistors thereof can beimproved.

Furthermore, in the transistor (each transmission gate TG), areas ofgate electrodes GE of an n-channel transistor should be the same.Furthermore, areas of gate electrodes GE of a p-channel transistorshould be the same. For example, the gate electrode GERp11 of thep-channel transistor of the transmission gate TGR11 and the gateelectrode GEBp11 of the p-channel transistor of the transmission gateTGB22 should be the same. If the areas of the gate electrodes GE aredifferent, capacitances of the gate electrodes GE become different aswell, and characteristics of transistors may possibly differ in each.The gate electrodes GE of the same area can even the characteristics ofthe transistor. The light shielding layers LS should have the same area.

In the signal line switch circuit ASW, it is suitable that the gateelectrodes GE of a p-channel transistor have the same area, or the lightshielding layers LS thereof have the same area. It is suitable that allof the gate electrodes GE and the light shielding layers LS of ann-channel transistor have the same area. It is suitable that the gateelectrodes of an n-channel transistor have the same area, or the lightshielding layers LS thereof have the same area. It is suitable that allof the gate electrodes GE and the light shielding layers LS of ap-channel transistor have the same area. Furthermore, it is moresuitable that the gate electrodes and the light shielding layers LS ofan n-channel transistor and the gate electrodes GE and the lightshielding layers LS of a p-channel transistor have the same area.

Note that, if they are formed in two common transistors as with the gateelectrode GEGp10 and the light shielding layer LSGp10, such electrodeand layer should have twice the area of other gate electrodes GE andlight shielding layers LS. For example, the area of the gate electrodeGEGp10 is twice the area of the gate electrode GERp11. Thus, thecapacitance of the gate electrode GE can be the same regardless of thetransistors.

Note that, in FIG. 4 , each source electrode of the transmission gate TGis illustrates as signal line SL for better understanding. A positionalrelationship between the source electrode SE and the signal line SL willbe described later.

In FIG. 4 , an extracting line WL1 includes a first portion WL1 s and asecond portion WL1 g. A extracting line WL2 includes a first portion WL2s and a second portion WL2 g. The first portion WL1 s of the extractingline WL1 and the first portion WL2 s of the extracting line WL2 are eachformed in the same line layer as with the connect line SNW (the sameline layer as with the signal line SL and the drain electrode DE of FIG.2B). The second portion WL1 g of the extracting line WL1 and the secondportion WL2 g of the extracting line WL2 are each formed in the sameline layer as with the gate electrode GE (same line layer as with thegate electrode GE of FIG. 2B). Note that, when it is not necessary tospecifically distinguish between the first portions WL1 s and WL2 s,they will be referred to as first portions WLs. When it is not necessaryto specifically distinguish between the second portions WL1 g and WL2 g,they will be referred to as second portions WLg.

Select lines xSS (a select line xSSR1, a select line xSSG1, a selectline xSSB1, a select line xSSR2, a select line xSSG2, and a select linexSSB2) are disposed between the connect line CNW and the first portionWLs of the extracting line WL. The connect line CNW and the firstportion WLs of the extracting line WL are formed in the same line layeras described above. Thus, the connect line CNW and the first portion WLsof the extracting line WL are necessary to be bridged by a differentline layer. Thus, the connect line CNW and the first portion WLs of theextracting line WL is connected by the second portion WLg in the samelayer as with the gate electrode GE.

Now, the transistors of the transmission gate TG will be explained. Then-channel transistor and the p-channel transistor of the transmissiongate TG are the transistors having similar cross-sectional structure.The transistor will be referred to as transistor TT. FIG. 7 is across-sectional view of the transistor TT.

The transistor TT of FIG. 7 has a cross-sectional structure similar tothat of the switching element PSW of the subpixel SX of FIG. 2B. Notethat, the light shielding layer LS of the transistor TT of FIG. 7 has ashape similar to the gate electrode GE as described above. That is, inthe example of FIG. 7 , an edge portion of the light shielding layer LSand an edge portion of the gate electrode GE match and conform to eachother.

Furthermore, the light shielding layer LS and the gate electrode GE arenot physically connected to each other. That is, the light shieldinglayer LS and the gate electrode GE do not contact each other. In thepresent embodiment, the light shielding layer LS functions as aso-called back gate, which is not physically connected to the gateelectrode GE (or the scan line GL), and is driven in a floating state.

With the light shielding layer LS which is a back gate provided with thetransistor TT, current flowing to the transistor T can be increased.Thus, characteristics of the transistor can be improved.

If the light shielding layer LS as a back gate is driven in a floatingstate, a potential applied to the light shielding layer LS can easily becontrolled by changing the potential of the gate electrode GE, the drainelectrode DE (the connect line CNW), and the source electrode (thesignal line SL).

Furthermore, a contact structure in which a light shielding layer LSfunctioning as a back gate physically contacts a gate electrode GE and aselect line SS is not adopted in this example, an area in which thesignal line switch circuit ASW is formed can be reduced.

Now, referring to FIG. 4 , a positional relationship between the gateelectrode GE, the select line SS, and the connect line will beexplained. The gate electrode GE of FIG. 4 is disposed to overlap theselect line SS. Furthermore, the gate electrode GE is disposed betweenadjacent select lines SS. The gate electrode GE may be disposed betweenthe select line SS and the connect line SNW adjacent to each other. FIG.8 is a plan view illustrating a part of FIG. 4 in an enlarged manner.

FIG. 8 omits the light shielding layer LS for easier understanding.However, as explained above with reference to FIG. 4 , in the signalline switch circuit ASW, provided is the light shielding layer LS ofsame shape as the gate electrode GE overlapping the gate electrode GE ina plan view. FIG. 8 illustrates, of the transmission gate TG of thesignal line switch circuit ASW, the gate electrode GE of the p-channeltransistor and the select line SS connected thereto. In FIG. 8 , THindicates a contact hole formed in the insulating layer ILI, and thegate electrode GE and the select line SS are connected together throughthe contact hole TH. Although this is not shown, the select line SS ofan n-channel transistor and the gate electrode GE are connected togetherthrough the contact hole TH.

The gate electrode GE of FIG. 8 includes, for example, a linear portionextending along the second direction Y and a projection portionprojecting from the linear portion and extending along the firstdirection X. Specifically, the gate electrode GERp11 includes a linearportion LRp11 and a projection portion BRp11. The linear portion LRp11extends along the second direction Y as mentioned above. The projectionportion BRp11 extends from the linear portion LRp11 along the firstdirection X. The projection portion BRp11 overlaps the select line xSSR1in a plan view.

A length (width) of the projection portion BRp11 in the second directionY may be longer than a length (width) of the linear portion LRp11 in thefirst direction X.

The gate electrode GEBp11 includes a linear portion LBp11 extendingalong the second direction Y, a projection portion BBp11 a extendingfrom the linear portion LGp11 in an opposite direction in the firstdirection X, and a projection portion BBp11 b extending from the linearportion LGp21 in an opposite direction in the first direction X. Theprojection portion BBp11 a is disposed between the connect line SNW1 andthe select line xSSR1. The projection portion BBp11 b overlaps theselect line xSSB1.

A length (width) of the projection portion BBp11 b in the seconddirection Y may be longer than a length (width) of the projectionportion BBp11 a in the second direction Y. A length (width) of theprojection portion BBp11 b in the second direction Y may be longer thana length (width) of the linear portion LBp11 in the first direction X.

The gate electrode GEGp21 includes a linear portion LGp21 extendingalong the second direction Y, a projection portion BGp21 a extendingfrom the linear portion LGp21 a in the opposite direction of the firstdirection X, a projection portion BGp21 b extending from the linearportion LGp21 along the first direction X, and a projection portionBGp21 c extending from the tip of the linear portion LGp1 along thefirst direction X. The projection portion BGp21 a and the projectionportion BGp21 b are disposed between the connect line SNW1 and theselect line xSSR1. The projection portion BGp21 c overlaps the selectline xSSG2.

A length (width) of the projection portion BGp21 c in the seconddirection Y may be longer than a length (width) of the projectionportion BGp21 a and the projection portion BGp21 b in the seconddirection Y. A length (width) of the projection portion BGp21 c in thesecond direction Y may be longer than a length (width) of the linearportion LGp21 in the first direction X.

The gate electrode GERp21 includes a linear portion LRp2 extending alongthe second direction Y and a projection portion BRp21 extending from atip of the linear portion LRp21 along the first direction X. Theprojection portion BRp21 overlaps the select line xSSR2.

A length (width) of the projection portion BRp21 in the second directionY may be longer than a length (width) of the linear portion LRp21 in thefirst direction X.

The gate electrode GEBp21 includes a linear portion LBp21 extendingalong the second direction Y, a projection portion BBp21 a extendingfrom the tip of the linear portion LBp21 in the first direction X, and aprojection portion BBp21 b extending from the tip of the linear portionLBp1 along the first direction X. The projection portion BBp21 a and theprojection portion BBp21 b overlap the select line xSSB2.

A length (width) of the projection portion BBp21 a and the projectionportion BBp21 b in the second direction Y may be longer than a length(width) of the linear portion LBp21 in the first direction X.

The gate electrode GEGp10 includes a linear portion LGp10 a and a linearportion LGp10 b, and a projection portion BGp10 a connecting the ends ofthe linear portions LGp10 a and LGp10 b and extending parallel to thefirst direction X. The gate electrode GE10 includes a linear portionLGp10 c extending along the second direction Y, a projection portionBGp10 b extending from the tip of the linear portion LGp10 c in anopposite direction of the first direction X, and a projection portionBGp10 c extending from the tip of the linear portion LGp10 c along thefirst direction X. The projection portion BGp10 b and the projectionportion BGp10 c overlap the select line xSSG1.

A length (width) of the projection portion BGp10 b and the projectionportion BGp10 c in the second direction Y may be longer than a length(width) of the linear portion LGp10 c in the first direction X.

Although explanation is omitted, each of the gate electrode GERp22, thegate electrode GEBp22, the gate electrode GEGp22, the gate electrodeGERp12, and the gate electrode GEBp12 includes linear portions andprojection portions in a similar manner as above.

Furthermore, as shown in FIGS. 4 and 6 , since the gate electrode GE andthe light shielding layer LS are shaped similarly, the light shieldinglayer LSRp11, the light shielding layer LSBp11, the light shieldinglayer LSGp21, the light shielding layer LSRp21, the light shieldinglayer LSBp21, the light shielding layer LSp10, the light shielding layerLSBp22, the light shielding layer LSRp22, the light shielding layerLSGp22, the light shielding layer LSBp12, and the light shielding layerLSBp12 each have linear portions and projection portions in a similarmanner as in FIG. 8 .

For example, the linear portion LGp10 c of the gate electrode Gp21 willbe referred to as first linear portion, and the projection portion BGp10b and the projection portion BGp10 c will be referred to as firstprojection portions. An area of the light shielding layer LSGp10overlapping the linear portion LGp10 c will be referred to as secondlinear portion, and an area thereof overlapping the projection portionBGp10 b and the projection portion BGp10 c will be referred to as asecond projection portion. The first projection portion and the secondprojection portion overlap the select line xSSG which is at least oneselect line.

The projection portion BGp10 a extending from the linear portion LGp10 cas the first linear portion in parallel to the first direction X will bereferred to as a third projection portion. The area of the lightshielding layer LSGp10 overlapping the projection portion BGp10 a willbe referred to as a fourth projection portion. The third projectionportion and the fourth projection portion are disposed between theconnect electrode CNW1 (or the connect electrode CNW2) and the selectline xSSB2.

FIG. 9 is a plan view illustrating a portion of FIG. 4 in an enlargedmanner. FIG. 9 illustrates a gate electrode GE of an n-channeltransistor and a select line SS connected thereto of the transmissiongate TG of the signal line switch circuit ASW.

The gate electrode GE of an n-channel transistor and the light shieldinglayer LS of FIG. 9 have substantially the same shape. However, a portionof the gate electrode GE and the light shielding layer LS have portionsshaped differently. FIG. 10 is a plan view illustrating the gateelectrode and the light shielding layer. Note that, in FIG. 10 , thegate electrode GE is depicted in a solid line, and the light shieldinglayer LS is depicted in a dotted line and is hatched.

In the signal line switch circuit ASW of FIG. 10 , the gate electrodeGEGn21 and the light shielding layer LSGn21 have the same shape, and thesame applies to the gate electrode GERn21 and the light shielding layerLSRn21, the gate electrode GEBn21 and the light shielding layer LSBn21,the gate electrode GEBn22 and the light shielding layer LSBn22, the gateelectrode GERn22 and the light shielding layer LSRn22, and the gateelectrode GEGn22 and the light shielding layer LSGn22.

On the other hand, the gate electrode GERn11 and the light shieldinglayer LSRn11 have similar shapes but do not have a perfectly-same shape,and the same applies to the gate electrode GEBn21 and the lightshielding layer LSBn21, the gate electrode GEGn11 and the lightshielding layer LSGn11, the gate electrode GERn22 and the lightshielding layer LSRn22, and the gate electrode GEBn12 and the lightshielding layer LSBn12.

However, for example, the areas of the gate electrode GE and the lightshielding layer LS are the same in the gate electrode GE and the lightshielding layer LS of FIG. 10 regardless of the transistor TT. Forexample, even though the gate electrode GERn11 and the light shieldinglayer LSRn11 do not have a perfectly-same shape, but the areas of thegate electrode GERn11 and the light shielding layer LSRn11 are the sameby adjusting, for example, a line width of the gate electrode GRRn11 andthe light shielding layer LSRn11. Thus, the gate electrode Tn11 and thegate electrode GEGn11 have the same area, and furthermore, the lightshielding layer LSRn11 and the light shielding layer LSGn11 have thesame area, and the gate electrode GE and the light shielding layer LShave the same area regardless of the transistor TT.

Now, the signal line SL will be explained. The signal line SL of FIG. 9includes a first portion SLs, a second portion SLg, and a sourceelectrode SE. The source electrode depicted as the signal line SL inFIG. 4 is the source electrode SE of FIG. 9 .

In FIG. 9 , the signal line SLR11 includes a first portion SLR11 s,second portion SLR11 g, and source electrode SER11 which is a drain ofthe transmission gate TGR11. The first portion SLR11 s and the sourceelectrode SER11 are formed in the same line layer as with the selectline SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLR11 g is formed in the sameline layer as with the gate electrode GE.

The first portion SLR11 s of the signal line SLR11 and the sourceelectrode SER11 are formed in the same line layer as with the selectline SS as mentioned above. Thus, in the area where the select line SSis arranged, a bridge by another line layer is required. Thus, in thearea where the select line SS is arranged, the second portion SLR11 g inthe same layer as with the gate electrode GE connects between the firstportion SLR11 s of the signal line SLR11 and the source electrode SER11.The same applies to the other signal lines SL.

The signal line SLB11 includes a first portion SLB11 s, a second portionSLB11 g, and a source electrode SEB11. The first portion SLB11 s and thesource electrode SEB11 are formed in the same line layer as with theselect line SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLB11 g is formed in the sameline layer as with the gate electrode GE.

The signal line SLG21 includes a first portion SLG21 s, a second portionSLG21 g, and a source electrode SEG21. The first portion SLG21 s and thesource electrode SEG21 are formed in the same line layer as with theselect line SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLG21 g is formed in the sameline layer as with the gate electrode GE.

The signal line SLR21 includes a first portion SLR21 s, a second portionSLR21 g, and a source electrode SER21. The first portion SLR21 s and thesource electrode SER21 are formed in the same line layer as with theselect line SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLR21 g is formed in the sameline layer as with the gate electrode GE.

The signal line SLB21 includes a first portion SLB21 s, a second portionSLB21 g, and a source electrode SEB21. The first portion SLB21 s and thesource electrode SEB21 are formed in the same line layer as with theselect line SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLB21 g is formed in the sameline layer as with the gate electrode GE.

The signal line SLG11 includes a first portion SLG11 s, a second portionSLG11 g, and a source electrode SEG11. The first portion SLG11 s and thesource electrode SEG11 are formed in the same line layer as with theselect line SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLG11 g is formed in the sameline layer as with the gate electrode GE.

The signal line SLG12 includes a first portion SLG12 s, a second portionSLG12 g, and a source electrode SEG12. The first portion SLG12 s and thesource electrode SEG12 are formed in the same line layer as with theselect line SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLG12 g is formed in the sameline layer as with the gate electrode GE.

The signal line SLB22 includes a first portion which is not shown, asecond portion SLB22 g, and a source electrode SEB22. The first portionwhich is not shown and the source electrode SEB22 are formed in the sameline layer as with the select line SS, the connect line CNW, and thefirst portion WLs of the extracting line WL. The second portion SLB22 gis formed in the same line layer as with the gate electrode GE.

The signal line SLR22 includes a first portion SLR22 s, a second portionSLR22 g, and a source electrode SER22. The first portion SLR22 s and thesource electrode SER22 are formed in the same line layer as with theselect line SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLR22 g is formed in the sameline layer as with the gate electrode GE.

The signal line SLG22 includes a first portion which is not shown, asecond portion SLG22 g, and a source electrode SEG22. The first portionwhich is not shown and the source electrode SEG22 are formed in the sameline layer as with the select line SS, the connect line CNW, and thefirst portion WLs of the extracting line WL. The second portion SLG22 gis formed in the same line layer as with the gate electrode GE.

The signal line SLR12 includes a first portion SLR12 s, a second portionSLR12 g, and a source electrode SER12. The first portion SLR12 s and thesource electrode SER12 are formed in the same line layer as with theselect line SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLR12 g is formed in the sameline layer as with the gate electrode GE.

The signal line SLB12 includes a first portion SLB12 s, a second portionSLB12 g, and a source electrode SEB12. The first portion SLB12 s and thesource electrode SEB12 are formed in the same line layer as with theselect line SS, the connect line CNW, and the first portion WLs of theextracting line WL. The second portion SLB12 g is formed in the sameline layer as with the gate electrode GE.

The shapes and arrangements of the linear portions and the projectionportions of the gate electrode GE and the light shielding layer LS havebeen explained above; however, the present embodiment is not limited tothe aforementioned example. The gate electrode GE and the lightshielding layer LS should include a projection portion projecting from alinear portion. It is suitable that the projection portion is arrangedin a position overlapping the select line SS, between adjacent connectline CNW and select line SS, or between adjacent select lines SS. Withsuch arrangement of the projection portion, a capacitance of the gateelectrode GE and the light shielding layer LS can be secured greatly,and thus, characteristics of the transistor can be improved.

However, as described above, in each transistor (each transmission gateTG), it is suitable that the gate electrodes GE have the same area. In ap-channel transistor, it is suitable that the gate electrodes GE or thelight shielding layers have the same area. In an n-channel transistor,it is suitable that the gate electrodes GE or the light shielding layershave the same area. In each of an n-channel and a p-channel transistors,it is suitable that the gate electrodes GE or the light shielding layershave the same area.

With the gate electrodes GE and the light shielding layers LS having thesame area, the capacitances of the gate electrode GE and the lightshielding layer LS will be the same. Thus, characteristics of eachtransistor can be uniformed.

With the present embodiment, the capacitance of the gate electrode GEand the capacitance of the light shielding layer LS can be the same. Byproviding the linear portion and the projection portion with each of thegate electrode GE and the light shielding layer LS and using the lightshielding layer LS as a back gate, current flowing to the transistor TT(transmission gate TG) can be increased. Furthermore, with the gateelectrode GE and the light shielding layer LS of each transistor Thaving the same area, unevenness in the transistors TT can bepreventable. Thus, characteristics of the signal line switch circuit ASWcan be improved. Furthermore, display quality of the display device DSPcan be improved.

Structural Example

FIG. 11 is a plan view illustrating another structural example of theembodiment. In the structural example of FIG. 11 , as compared to theexample of FIG. 4 , a different transistor is adopted in a signal lineswitch circuit.

A signal line switch circuit ASW of FIG. 11 includes three transmissiongates electrically connected to one extracting line WL. That is, imagesignals are input to three signal lines SL through one extracting lineWL.

FIG. 12 is a circuit diagram of the signal line switch circuit of FIG.11 . In FIGS. 11 and 12 , a drain of a transmission gate TGR1 isconnected to a signal line SLR1 as a source of the signal line SLR1. Thesource of the transmission gate TGR1 is connected to a connect lineCNW1. A gate electrode GERn1 of an n-channel transistor of thetransmission gate TGR1 is connected to a select line SSR. A gateelectrode GERp1 of a p-channel transistor of the transmission gate TGR1is connected to a select line xSSR.

A drain of a transmission gate TGG1 is connected to a signal line SLG1as a source of the signal line SLG1. The source of the transmission gateTGG1 is connected to the connect line CNW1. A gate electrode GEGn1 of ann-channel transistor of the transmission gate TGG1 is connected to aselect line SSG. A gate electrode GEGp1 of a p-channel transistor of thetransmission gate TGG1 is connected to a select line xSSG.

A drain of a transmission gate TGB1 is connected to a signal line SLB1as a source of the signal line SLB1. The source of the transmission gateTGB1 is connected to the connect line CNW1. A gate electrode GEBn1 of ann-channel transistor of the transmission gate TGB1 is connected to aselect line SSB. A gate electrode GEBp1 of a p-channel transistor of thetransmission gate TGB1 is connected to a select line xSSB.

A drain of a transmission gate TGR2 is connected to a signal line SLR2as a source of the signal line SLR2. The source of the transmission gateTGR2 is connected to a connect line CNW2. A gate electrode GERn2 of ann-channel transistor of the transmission gate TGR2 is connected to theselect line SSR. A gate electrode GERp2 of a p-channel transistor of thetransmission gate TGR2 is connected to the select line xSSR.

A drain of a transmission gate TGG2 is connected to a signal line SLG2as a source of the signal line SLG2. The source of the transmission gateTGG2 is connected to the connect line CNW2. A gate electrode GEGn2 of ann-channel transistor of the transmission gate TGG2 is connected to theselect line SSG. A gate electrode GEGp2 of a p-channel transistor of thetransmission gate TGG2 is connected to the select line xSSG.

A drain of a transmission gate TGB2 is connected to a signal line SLB2as a source of the signal line SLB2. The source of the transmission gateTGB2 is connected to the connect line CNW2. A gate electrode GEBn2 of ann-channel transistor of the transmission gate TGB2 is connected to theselect line SSB. A gate electrode GEBp2 of a p-channel transistor of thetransmission gate TGB2 is connected to the select line xSSB.

The n-channel transistor of each of the transmission gate TGR1 and thetransmission gate TGG11 is formed using a semiconductor layer SCn1. Then-channel transistor of the transmission gate TGB1 is formed using asemiconductor layer SCn2. The n-channel transistor of each of thetransmission gate TGR2 and the transmission gate TGG2 is formed using asemiconductor layer SCn3. The n-channel transistor of the transmissiongate TGB2 is formed using a semiconductor layer SCn4.

The p-channel transistor of each of the transmission gate TGR1 and thetransmission gate TGG11 is formed using a semiconductor layer SCp1. Thep-channel transistor of the transmission gate TGB1 is formed using asemiconductor layer SCp2. The p-channel transistor of each of thetransmission gate TGR2 and the transmission gate TGG2 is formed using asemiconductor layer SCp3. The p-channel transistor of the transmissiongate TGB2 is formed using a semiconductor layer SCp4.

The signal line switch circuit ASW of FIG. 11 includes a light shieldinglayer LS overlapping a gate electrode GE, similar to the embodiment. Inthe present example, it is preferable that the gate electrode GE and thelight shielding layer LS overlapping each other have the same shape.

Furthermore, it is preferable that the gate electrodes GE of then-channel transistor have the same area. Furthermore, it is preferablethat the gate electrodes GE of the p-channel transistor have the sameshape. Furthermore, it is preferable that the light shielding layers LShave the same area.

FIG. 13 is a plan view of the gate electrode of FIG. 11 . FIG. 14 is aplan view of the light shielding layer LS of FIG. 11 . With respect tothe p-channel transistor, the gate electrode GE and the light shieldinglayer LS overlapping each other have the same shape and the same area.

FIG. 15 illustrates a portion of FIG. 11 in an enlarged manner.Specifically, FIG. 15 is an enlarged view of an area where the p-channeltransistor is disposed. In FIG. 15 , for easier understanding, the lightshielding layer LS is omitted.

As shown in FIG. 15 , the gate electrode GE includes, for example, alinear portion extending along the second direction Y and a projectionportion projecting from the linear portion and extending along the firstdirection X.

A gate electrode GERp1 of FIG. 15 includes a linear portion LGp1extending along the second direction Y, and a projection portion BRp1connecting to a linear portion LRp1. The projection portion BRp1 extendsin an opposite direction of the first direction X. The projectionportion BRp1 overlaps a select line xSSR in a plan view.

A gate electrode GEGp1 includes a linear portion LGp1 and a projectionportion BGp1 a and a projection portion BGp1 b. The linear portion LGp1extends along the second direction Y. The projection portion BGp1 aextends from the linear portion LGp1 in an opposite direction of thefirst direction X. The projection portion BGp1 b is connected to theprojection portion BGp1 a, and extends from the projection portion BGp1a in the opposite direction of the first direction X. A length (width)of the projection portion Bp1 a in the second direction Y is longer thana length (width) of the projection portion BGp1 b in the seconddirection Y. The projection portion BGp1 a and the projection portionBGp1 b overlap a select line xSSR1 in a plan view.

A gate electrode GEBp1 includes a linear portion LBp1 extending alongthe second direction Y and a projection portion BBp1 connecting to thelinear portion LBp1. The projection portion BBp1 extends in parallel tothe first direction X. The projection portion BBp1 overlaps the selectline xSSR in a plan view.

Note that, the gate electrode GERp2, the gate electrode GEGp2, and thegate electrode GEBp2 are shaped similarly to the gate electrode GERp1,the gate electrode GEGp1, and the gate electrode GEBp1, respectively,and are arranged similarly as well. Thus, the descriptions with respectto the gate electrode GERp2, the gate electrode GEGp2, and the gateelectrode GEBp2 are the same as those with respect to the gate electrodeGERp1, the gate electrode GEGp1, and the gate electrode GEBp1, and thedetailed descriptions will be omitted here.

FIG. 16 illustrates a portion of FIG. 11 in an enlarged manner.Specifically, FIG. 16 is an enlarged view of an area where the n-channeltransistor is disposed. In FIG. 16 , for easier understanding, the lightshielding layer LS is omitted. Note that, as in FIGS. 11, 13, and 14 ,the light shielding layer LS is shaped substantially the same as withthe gate electrode GE.

In FIG. 16 , a signal line SLR1 includes a first portion which is notshown, a second portion SLR1 g, and a source electrode SER1. The firstportion which is not shown is connected to the second portion SLR1 g.The first portion and the source electrode SER1 are formed in the sameline layer as with the select line SS, the connect line CNW, and thefirst portion WLs of the extracting line WL. The second portion SLR1 gis formed in the same line layer as with the gate electrode GE.

A signal line SLG1 includes a first portion SLG1 s, a second portionSLG1 g 1, a third portion SLG1 g 2, and a source electrode SEG1. Thefirst portion SLG1 s connects the second portion SLG1 g 1 and the thirdportion SLG1 g 2. The first portion SLG1 s and the source electrode SEG1are formed in the same line layer as with the select line SS, theconnect line SNW, and the first portion WLs of the extracting line WL.The second portion SLG1 g 1 and the third portion SLG1 g 2 are formed inthe same line layer as with the gate electrode GE. Note that the thirdportion SLG1 g 2 is further connected to a fourth portion (which is notshown) in the same line layer as with the first portion SLG1 s.

A signal line SLB1 includes a first portion which is not shown, a secondportion SLB1 g, and a source electrode SEB1. The first portion which isnot shown is connected to the second portion SLB1 g. The first portionand the source electrode SEB1 are formed in the same line layer as withthe select line SS, the connect line CNW, and the first portion WLs ofthe extracting line WL. The second portion SLB1 g is formed in the sameline layer as with the gate electrode GE.

Note that, connection relationships of the signal line SLR2, the signalline SLG2, and the signal line SLB2 are similar to those of the signalline SLR1, the signal line SLG1, and the signal line SLB1, respectively.Thus, the descriptions of the signal line SLR2, the signal line SLG2,and the signal line SLB2 are the same as those of the signal line SLR1,the signal line SLG1, and the signal line SLB1, and the detaileddescription will be omitted here.

In the example of FIG. 1 , similar to the example of FIG. 9 , the signalline SL has a portion to be replace with the same line layer as with thegate electrode GE in order to bridge the select line SS.

In the present example, the advantages obtained by the embodiment can beachieved.

Comparative Example

FIG. 17 is a plan view of a structural example of a comparative example.In the comparative example of FIG. 17 , as compared to the structuralexample of FIG. 4 , a light shielding layer is not shaped similar to agate electrode, the gate electrode and the light shielding layer havedifferent areas with respect to each transistor, and the gate electrodeand the light shielding layer do not include a projection portion.

Referring to FIG. 17 and FIGS. 18A and 18B, the comparative example willbe explained. FIGS. 18A and 18B are plan views illustrating the gateelectrode and the light shielding layer, respectively, in a signal lineswitch circuit of FIG. 17 . FIG. 18A is a plan view of the gateelectrode GE of the comparative example, and FIG. 18B is a plan view ofthe light shielding layer LS of the comparative example. Although thisis not shown, the light shielding layer LS overlaps correspondingsemiconductor layer SC and gate electrode GE in a plan view. Note that,FIGS. 17, 18A, and 18B illustrate an area where the p-channel transistoris disposed.

As in FIGS. 17, 18A, and 18B, the signal line switch circuit ASW of thecomparative example includes the light shielding layer LS with a shapewhich is different from that of the gate electrode GE. Furthermore, inthe signal line switch circuit ASW of FIGS. 17, 18A, and 18B, the gateelectrodes GE have different areas. Furthermore, the gate electrode GEand the light shielding layer LS do not include a projection portion.

Note that, as in FIG. 18B, light shielding layers corresponding to thegate electrode GEGp10 are the light shielding layer LSGp11 and the lightshielding layer LSGp12.

As compared to the comparative example of FIGS. 17, 18A, and 18B, in theaforementioned embodiment, the capacitance of the gate electrode GE andthe capacitance of the light shielding layer LS can be the same. Withlinear portions and projection portions of each of the gate electrode GEand the light shielding layer LS, current flowing to the transistor TTcan be increased. Furthermore, with the gate electrodes GE of thetransistor TT having the same area, uniformity of the transistors TT ispossible. Thus, characteristics of the signal line switch circuit ASWcan be improved. Furthermore, the display device DSP of the embodimentcan improve the display quality.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A display device comprising: a plurality ofsignal lines; a switch circuit connected to the signal lines; and aplurality of select lines extending in a first direction and arranged ina second direction, the plurality of select lines being connected to theswitch circuit, wherein the switch circuit includes a plurality oftransistors connected to the plurality of the signal lines, theplurality of transistors include a plurality of gate electrodes and aplurality of light shielding layers overlapping the plurality of gateelectrodes, each of the plurality of the select lines is connected toeach of the plurality of gate electrodes, at least one of the gateelectrodes includes a first linear portion extending along the seconddirection, and a first projection portion projecting from the firstlinear portion and extending along the first direction, at least one ofthe first light shielding layers includes a second linear portionextending along the second direction, and a second projection portionprojecting from the second linear portion and extending along the firstdirection, the first linear portion overlaps the second linear portion,the first projection portion overlaps the second projection portion, andthe first projection portion and the second projection portion overlapat least one of the plurality of select lines.
 2. The display deviceaccording to claim 1, wherein each of the light shielding layers doesnot contact the overlapping gate electrode.
 3. The display deviceaccording to claim 1, wherein the light shielding layer is a back gateof the transistor, and is driven in a floating state.
 4. The displaydevice according to claim 3, further comprising a connect lineconnecting sources of the plurality of transistors, wherein each of theplurality of select lines is connected to each of the plurality of gateelectrodes, the gate electrode having the first projection portionincludes a third projection portion projecting from the first linearportion and extending along the first direction, the light shieldinglayer having the second projection portion includes a fourth projectionportion extending from the second linear portion and extending along thefirst direction, and the third projection portion and the fourthprojection portion overlap with each other between the connection lineand one of the plurality of select lines.
 5. The display deviceaccording to claim 4, wherein the transistor is a transmission gateincluding an n-channel transistor and a p-channel transistor.